The present invention relates to tools used in the drilling and completion of oil wells. In particular, the invention relates to a tool that can be used to reduce friction between a liner and a well bore or to release a drill string for its removal from a well bore.
In the drilling of oil wells, a drill string is used to drill a well hole. After the well hole is drilled, casing or liner is run across the productive interval by drill pipe. With the liner in place, cement is pumped down through the drill pipe, through the liner and into an annulus between the liner and a casing in the well hole wall to cement the liner in place and to keep production fluids in the liner.
Quite often, well holes are not completely vertical. They can have substantial horizontal components. Wells with substantial horizontal components are called high angle, extended reach wells. Running the liner through high angle, extended reach well holes can be difficult because of friction between the liner and the well hole wall caused by the weight of the liner against the wall. Translational friction can be substantially reduced by rotating the liner while it is being run into the well hole.
The tools that run liners into well holes have not been able to rotate the liners while they were being run in, although the tools permit liner rotations during cementing. A reason for this is that rotation is used to release the tools from the liners once the liners are in place. Consequently, it has not been possible to rotate the liners to reduce frictional drag.
Sometimes during the drilling of a well a drill string has to be pulled from the well hole because something in the leading end of the string gets stuck. To pull the string requires disconnecting it from the stuck portion. Typically, the disconnection is done by applying left hand torque to the drill string in order to unscrew a connection at some arbitrary point within the drill pipe.